Real Madrid has much better finances and it is possible that Haaland will be their target next season.
Real Madrid to go for Haaland? After signing Mbappe you say? I don't think so honestly.
Because they don't need a player like Haaland anymore after this signing. Mbappe will most probably play in the centre-forward position which means they won't need another star striker. They don't have the same play style of course but Real Madrid would prefer Mbappe to Haaland for sure considering the way they play. 
Besides Real Madrid is full of star players. Let's say they signed Haaland as well. Then how will Ancelotti deal with this? There are many great alternatives for the attacking line. He can't just cut any of them easily.
I want to laugh reading it, because Haaland is not really noticed in my opinion, Ancelotti might not think of including him in the squad, although it is possible, and making Haaland in the center of their striker position while Mbappe is next to him to run and pass, but is it possible for them to be humble, I think there will be ego centricity that will be generated when they are together on the other hand also both hunt to be the best player.
Really this is just ridiculousness, the youth is so good and I prefer Mbappe to Haaland, however as you said Mbappe could be more perfect for Real Madrid's style of play, If you also note that Haaland was not so productive at the end of last season.